ANSI/ASHRAE Standard 135-2001, BACnet--A Data Communication Protocol for Building Automation and Control Networks, is the only open, consensus-developed standard in the building controls industry.

Addenda 135a, c and d were approved for publication at ASHRAE's 2004 Winter Meeting held in Anaheim, CA, Jan. 24-28.

Addendum 135a changes the way schedules are represented and maintained in BACnet systems.

BACnet always has had the capability to represent even very complex schedules, according to Steve Bushby, chair of the committee. However, if a schedule represents the combination of several independent events, it has not been possible for a workstation to read the schedule object information and determine the individual components that were combined to make the overall schedule. The features in 135a make it possible to view and manipulate the schedules at this finer level of detail, he said.

Addendum c contains eight new features that include enhancements to the life safety objects and services and the ability to represent utility meters and other measuring devices that provide pulsed outputs.

Addendum d contains information on how to interconnect BACnet devices with devices that use the EIB/Konnex protocol.

The addenda are subject to a 15-day appeals period to the Board of Directors. Published addenda to ASHRAE standards are available for free at www.ashrae.org.